The object is to study the immunologic responses directed against tumor-specific antigens during the development of human bladder cancer. Workers in the dyestuffs industry exposed to the carcinogens alpha and beta naphthylamine before 1952 will be studied at regular intervals over a five-year period. It is anticipated that during this period, a significant number of new cases should arise in the population considered to be at "great risk". Lymphocytotoxicity, complement-mediated serum cytotoxicity, and blocking factor activity will be examined against a panel of allogeneic bladder cancers on each occasion. The results of these tests will be evaluated along with data obtained by regular examination of urine for red cells and, where appropriate, more detailed examination of the urinary tract including biopsy. It should be possible to determine the time relationships of the development of lymphocytotoxicity, serum antibody, blocking factor and overt tumor. It is possible that these studies may provide earlier diagnosis and an index of prognosis in carcinogen-induced bladder cancer.